An apparent clerical error has prompted judges to postpone the long-awaited war crimes trial of former Bosnian Serb military leader Ratko Mladic, possibly for months.

The delay cast a shadow over one of the court's biggest cases - and over the reputation of the court itself, whose most prominent trials have proceeded at a snail's pace.

It also highlighted problems faced by international tribunals in prosecuting sweeping indictments covering allegations of atrocities spanning years in countries far from the courts where defendants face justice.

"It is fraught with delay because of the volume of documentation and scope of alleged crimes," said Richard Dicker, the director of Human Rights Watch's international justice programme.

Presiding judge Alphons Orie said he was delaying the Yugoslav war crimes tribunal case due to "significant disclosure errors" by prosecutors, who are obliged to share all evidence with Mladic's lawyers.

Mr Orie said judges will analyse the "scope and full impact" of the error and aim to establish a new starting date "as soon as possible." The presentation of evidence was supposed to begin later this month.

Prosecutors had already acknowledged the errors and did not object to the delay. Mladic's lawyer has asked for a six-month delay to study the materials.

Mladic is accused of commanding Bosnian Serb troops who waged a campaign of murder and persecution to drive Muslims and Croats out of territory they considered part of Serbia during Bosnia's 1992-95 war.

His troops rained shells and snipers' bullets down on civilians in the 44-month siege of the Bosnian capital, Sarajevo. They also executed thousands of Muslim men and boys in Srebrenica, the site of Europe's worst massacre since the Second World War. He has refused to enter pleas to the charges but denies wrongdoing. If convicted, he faces a maximum sentence of life imprisonment.

Court spokeswoman Nerma Jelacic said much of the material that the defence did not get was about witnesses prosecutors had intended to call to testify before the court's summer break. Prosecutors acknowledged that the error "could impact on the fairness of the trial to the accused," she said.